In this talk we present an exact approach to calculating the entanglement entropy in spin chains that are described by conformal theory at quantum criticality. The method was initially used to study entanglement in free fermions and the XY model, but it turns out that Kitaev chains with long-ranged power law interactions also fall in the same solvable class. We evaluate the Schmidt gap in the entanglement spectrum and use it to map out the phase diagram of the model. Conformal features about the quantum critical line reveal how the universal scaling relations are affected by the power law exponent of the interactions.
}, author = {Francis N. C. Paraan and Cleofe Dennielle P. Ayang-ang} } @article {541, title = {Selective capture of CO$_{2}$ over N$_{2}$ and CH$_{4}$: B clusters and their size effects}, journal = {Mater. Today Commun.}, volume = {22}, year = {2020}, pages = {100712}, abstract = {Using density-functional theory (DFT), we investigate the selectivity of adsorption of CO$_{2}$ over N$_{2}$ and CH$_{4}$ on planar-type B clusters, based on our previous finding of strong chemisorption of CO$_{2}$ on the B$_{1}$$_{0}$$_{-}$$_{1}$$_{3}$ planar and quasiplanar clusters. We consider the prototype B$_{8}$ and B$_{1}$$_{2}$ planar-type clusters and perform a comparative study of the adsorption of the three molecules on these clusters. We find that, at room temperature, CO$_{2}$ can be separated from N$_{2}$ by selective binding to the B$_{1}$$_{2}$ cluster and not to the B$_{8}$ cluster. Selective adsorption of CO$_{2}$ over CH$_{4}$ at room temperature is possible for both clusters. Based on our DFT-adsorption data (including also a semi-infinite Boron sheet) and the available literature-adsorption value for N$_{2}$ on the planar-type B$_{3}$$_{6}$ cluster, we discuss the selectivity trend of CO$_{2}$ adsorption over N$_{2}$ and CH$_{4}$ with planar-cluster size, showing that it extends over sizes including B$_{1}$$_{0}$$_{-}$$_{1}$$_{3}$ clusters and significantly larger.}, doi = {10.1016/j.mtcomm.2019.100712}, url = {https://www.sciencedirect.com/science/article/abs/pii/S2352492819305719}, author = {Alexandra B. Santos-Putungan and Nata{\v s}a Stoji{\'c} and Nadia Binggeli and Francis N. C. Paraan} } @inproceedings {545, title = {Using YOLOv3 to detect colorectal polyps in video}, booktitle = {Proceedings of the 38th Samahang Pisika ng Pilipinas Physics Conference}, year = {2020}, month = {19{\textendash}23 Oct 2020}, pages = {SPP-2020-2A-05}, address = {Presented online}, abstract = {A model based on the You Only Look Once (YOLO) algorithm was trained to detect polyps on a dataset of 503 polyp-positive images taken from colonoscopy video frames. We achieve precision on test sets that is comparable to the performance of a previously described model trained on a much larger set of 5,545 images. However, our model has a lower recall and missed some polyps in the test set.}, url = {https://paperview.spp-online.org/proceedings/article/view/SPP-2020-2A-05}, author = {Mary Chris R. Go and Francis N. C. Paraan} } @inproceedings {gomcSPP2019, title = {Classification of chest radiographs using depthwise separable convolution}, booktitle = {Proceedings of the 37th Samahang Pisika ng Pilipinas Physics Conference}, year = {2019}, month = {29 May 2019}, pages = {SPP-2019-PA-21}, address = {Tagbilaran City, Philippines}, abstract = {Pneumonia x-ray images were classified using a neural network with depthwise separable convolutions. Each image was divided into three vertical regions and convolutions were applied to each region independently. The training model has less training parameters than a standard convolutional neural network (CNN) so that the tendency for overfitting and overall computation time is reduced. The trained network features a relatively high precision (ratio of true and predicted positives) and a significantly shorter training time than a conventional CNN. Our preliminary results indicate that the precision of the neural network was not greatly affected by the introduction of depthwise separable convolutions.}, url = {https://paperview.spp-online.org/proceedings/article/view/SPP-2019-PA-21}, author = {Mary Chris R. Go and Francis N. C. Paraan} } @inproceedings {medranoSPP2019, title = {Computational fluid dynamics analysis of downforce and drag generated by an accessory flat plate wing on the Teardrop 2.0}, booktitle = {Proceedings of the 37th Samahang Pisika ng Pilipinas Physics Conference}, year = {2019}, month = {29 May 2019}, pages = {SPP-2019-PB-50}, address = {Tagbilaran City, Philippines}, abstract = {We use computational fluid dynamics to calculate the hydrodynamic downforce generated by an accessory flat plate wing when attached to a model of the Teardrop 2.0 submersible. The Teardrop 2.0 is a towed submersible device used to survey shallow coral reefs. In operation, the Teardrop 2.0 can experience unintended changes in depth due to lift and cable tension from drag. In this study, a full scale computer generated reconstruction of the Teardrop 2.0 is fitted with a flat plate wing. This model is then subjected to fluid tunnel simulations using CFD software. At fixed operating speeds, the modified Teardrop 2.0 is found to increase in downforce and drag. Despite this increase in drag, the addition of the accessory wing is found to lower the drag-to-downforce ratio of the Teardrop 2.0 from 8.5 to 2.7, showing that the accessory wing increases downforce more than it increases drag.}, url = {https://paperview.spp-online.org/proceedings/article/view/SPP-2019-PB-50}, author = {Matthew R. Medrano and Francis N. C. Paraan} } @article {531, title = {Controlling the nucleophilic properties of cobalt salen complexes for carbon dioxide capture}, journal = {RSC Adv.}, volume = {9}, year = {2019}, pages = {23254}, abstract = {The nucleophilic properties of cobalt salen complexes are examined using density functional theory to investigate its carbon fixing capacity. In particular, carbon dioxide attack on neutral and anionic cobalt salen molecules is considered. Carbon fixation occurs for the anionic cobalt salen complex and is due to the nucleophilic interaction between the cobalt center and carbon dioxide molecule in a Co dz{\texttwosuperior}{\textendash}CO$_{2}$ π* interaction. A minimum energy path search by a nudged elastic band calculation reveals a lower forward activation energy for the anionic complex than the neutral complex, indicating that the formation of the anionic complex is thermodynamically and kinetically favored. In this case, the CO$_{2}$ molecule is chemisorbed as partial charge transfer from the cobalt center to carbon dioxide is observed. Proposed reaction mechanisms explain how the Co{\textendash}C bond energy of the CO$_{2}${\textendash}cobalt salen complex can be tuned by appropriate substitutions of electron donating or withdrawing groups on the phenyl ring.
}, doi = {10.1039/C9RA01990A}, author = {Meliton R. Chiong and Francis N. C. Paraan} } @inproceedings {esperanzaSPP2019, title = {Critical scaling at the N{\'e}el transition in an extended Hubbard model with Ising-like interaction}, booktitle = {Proceedings of the 37th Samahang Pisika ng Pilipinas Physics Conference}, year = {2019}, month = {29 May 2019}, pages = {SPP-2019-1G-05}, address = {Tagbilaran City, Philippines}, abstract = {We examine the critical behavior of the von Neumann entanglement entropy and the staggered magnetization order parameter in an extended Hubbard chain across the N{\'e}el transition at half-filling. The order parameter and the entanglement entropy was calculated using density matrix renormalization group (DMRG) for periodic chains with length L = 32, 64, and 100. We demonstrate that the entanglement entropy can locate the quantum critical point. Finite size scaling analyses of the N{\'e}el order parameter and entanglement entropy give estimates for the critical exponents associated with these observables.}, url = {https://paperview.spp-online.org/proceedings/article/view/SPP-2019-1G-05}, author = {Robertson C. Esperanza and Francis N. C. Paraan} } @inproceedings {gomezSPP2019, title = {Evaporation and compaction of colliding dust clusters at different impact parameters}, booktitle = {Proceedings of the 37th Samahang Pisika ng Pilipinas Physics Conference}, year = {2019}, month = {29 May 2019}, pages = {SPP-2019-PB-21}, address = {Tagbilaran City, Philippines}, abstract = {The dynamics of colliding dust clusters is important in the study of dust cloud evolution. In this work, a molecular dynamics simulation of the collision of two spherical clusters of SiO$_{2}$ particles was done to find out how the evaporation fraction depends on impact parameter. By measuring the average number of neighbors each unevaporated grain has, we found a critical impact parameter that results in maximum cluster compaction.}, url = {https://paperview.spp-online.org/proceedings/article/view/SPP-2019-PB-21}, author = {Jacob Gomez and Francis N. C. Paraan} } @inproceedings {535, title = {Ground state entanglement in an extended Hubbard model with Ising-like interactions}, booktitle = {AQIS Conference 2019 Abstract Booklet - Poster Day 1}, year = {2019}, month = {19{\textendash}23 Aug 2019}, pages = {164}, address = {Korea Institute for Advanced Study, Seoul}, abstract = {We probe the half-block von Neumann entanglement entropy along with the ground state properties of a 1D extended Hubbard model as its intrasite and intersite interaction parameters are varied. The half-block entanglement entropy was calculated using the density matrix renormalization group (DMRG) for a periodic chain. We demonstrate that the half-block entanglement entropy provides a sketch of the changes in the ground state of the system and that it can be used to locate the quantum critical lines in the model.}, url = {http://aqis-conf.org/2019/program/}, author = {Robertson C. Esperanza and Francis N. C. Paraan} } @inproceedings {lopezSPP2019, title = {Image preprocessing with bi-histogram equalization in a supervised classification of radiographs}, booktitle = {Proceedings of the 37th Samahang Pisika ng Pilipinas Physics Conference}, year = {2019}, month = {29 May 2019}, pages = {SPP-2019-PA-22}, address = {Tagbilaran City, Philippines}, abstract = {Convolutional neural network models are known for their effectiveness in solving computer vision problems. These neural networks are designed to extract features from raw data for accurate classification. The objective of this paper is to study the effects of bi-histogram equalization preprocessing on the performance of a convolutional neural network in identifying pneumonia from a chest x-ray image. The model trained with the preprocessed images demonstrated improved accuracy during training and validation of the neural network.}, url = {https://paperview.spp-online.org/proceedings/article/view/SPP-2019-PA-22}, author = {Vidal Wyatt M. Lopez and Francis N. C. Paraan} } @inproceedings {ongkikoSPP2019, title = {Molecular projected band structure of ammonia and ammonium adsorbed on graphene}, booktitle = {Proceedings of the 37th Samahang Pisika ng Pilipinas Physics Conference}, year = {2019}, month = {29 May 2019}, pages = {SPP-2019-PA-17}, address = {Tagbilaran City, Philippines}, abstract = {The electronic structures of ammonia and ammonium molecules adsorbed on pristine graphene are studied in this work. In particular, molecular projected densities of states (MolPDOS) were calculated by density functional theory to characterize these adsorption systems by projecting the eigenstates of the full system onto those of the adsorbate molecule. Ammonium adsorption on graphene exhibited a stronger adsorption than ammonia, indicating the possibility of designing a selective substrate. This difference was also reflected in the MolPDOS-produced band structure by the presence of distinct regions of mixed ammonium and graphene states located around 1 eV above the Fermi level.}, url = {https://paperview.spp-online.org/proceedings/article/view/SPP-2019-PA-17}, author = {Mario Antonio T. Ongkiko and Francis N. C. Paraan} } @inproceedings {castroSPP2019, title = {Multi-class semantic segmentation and volume calculation of cardiac CT scans using convolutional neural networks}, booktitle = {Proceedings of the 37th Samahang Pisika ng Pilipinas Physics Conference}, year = {2019}, month = {29 May 2019}, pages = {SPP-2019-1C-07}, address = {Tagbilaran City, Philippines}, abstract = {Computed tomography (CT) scans from the MICCAI 2017 Multi-Modality Whole Heart Segmentation Challenge dataset were segmented into seven anatomical substructures (left and right ventricles, left and right atria, myocardium, aorta, and pulmonary artery) using the SpatialConfiguration-Net (SCN). The SCN utilizes a U-Net convolutional network architecture that is designed for biomedical image segmentation. The performance of the neural network was evaluated by cross validation on the training data by the Dice Similarity Coefficient over all heart substructures. Improved segmentation of most of the substructures was observed over other proposed convolutional neural network pipelines. While the estimated volumes of the segmented substructures are consistent with the manual annotations, the SCN performed sub-optimally in detecting gaps between heart substructures due to the loss of resolution caused by multilayer down-sampling and up-sampling of the images.}, url = {https://paperview.spp-online.org/proceedings/article/view/SPP-2019-1C-07}, author = {Marc Jerrone Castro and Francis N. C. Paraan} } @inproceedings {deleonSPP2019, title = {Parallel acceleration of density matrix renormalization group calculations with TensorFlow}, booktitle = {Proceedings of the 37th Samahang Pisika ng Pilipinas Physics Conference}, year = {2019}, month = {29 May 2019}, pages = {SPP-2019-PB-14}, address = {Tagbilaran City, Philippines}, abstract = {We parallelize singular value decomposition in a matrix product state formulation of the density matrix renormalization group using the TensorFlow library to find use cases in which consumer-grade GPU hardware can reduce run times. Specifically, we tested the performance of the implementation on a 20-site spin chain for a variable number of kept states. We were able to acquire a speedup of up to 6.4\% when using TensorFlow GPU libraries and a speedup of up to 5.4\% with TensorFlow multicore CPU libraries. This speedup is observed when the number of kept states exceeds a threshold value so that the dimensions of the matrices in the calculation are large enough that the gains in parallelization exceed computational overhead costs.}, url = {https://paperview.spp-online.org/proceedings/article/view/SPP-2019-PB-14}, author = {Kryzz Joshua G. de Leon and Francis N. C. Paraan} } @inproceedings {536, title = {Quantum phase transitions and Schmidt gap closing in a Kitaev chain with long-ranged interactions}, booktitle = {AQIS Conference 2019 Abstract Booklet - Poster Day 1}, year = {2019}, month = {19{\textendash}23 Aug 2019}, pages = {174-175}, address = {Korea Institute for Advanced Study, Seoul}, abstract = {The quantum phase diagram of a generalized Kitaev chain that exhibits long-ranged hopping and pairing is mapped out by looking for sharp changes in the Schmidt gap of a ground state bipartition.Finite-size scaling analysis reveals that the Schmidt gap exhibits universal scaling behavior about the quantum critical lines. The critical exponents found shows that the model displays different properties at the long- and short-range limits of the interaction.}, url = {http://aqis-conf.org/2019/program/}, author = {Cleofe Dennielle P. Ayang-ang and Francis N. C. Paraan} } @article {498, title = {Strong chemisorption of CO$_{2}$ on B$_{1}$$_{0}${\textendash}B$_{1}$$_{3}$ planar-type clusters}, journal = {J. Phys. Condens. Matter}, volume = {31}, year = {2019}, pages = {145504}, abstract = {An ab initio density functional study was performed investigating the adsorption of CO$_{2}$ on neutral boron Bₙ (n = 10{\textendash}13) clusters that are characterized by planar and quasiplanar ground-state atomic structures. For all four clusters, we found large chemisorption binding energies, reaching 1.6 eV between CO$_{2}$ and B$_{1}$$_{2}$, with the adsorbed molecule oriented in the plane of the cluster and adsorbed along the cluster edge. A configuration with chemisorbed dissociated CO$_{2}$ molecule also exists for B$_{1}$$_{1}$ and B$_{1}$$_{3}$ clusters. The strong adsorption is due to the bending of the CO$_{2}$ molecule, which provides energetically accessible fully in-plane frontier molecular orbitals matching the edge states of the clusters. At the same time, the intrinsic dipole moment of a bent CO$_{2}$ molecule facilitates the transfer of excess electronic charge from the cluster edges to the molecule.
}, doi = {10.1088/1361-648x/aafebd}, author = {Alexandra B. Santos-Putungan and Nata{\v s}a Stoji{\'c} and Nadia Binggeli and Francis N. C. Paraan} } @conference {479, title = {Accuracy of a tensor network-based image classifier saturates with bond dimension}, year = {2018}, month = {18{\textendash}19 June 2018}, pages = {P126}, publisher = {ASTHRDP Graduate Scholars{\textquoteright} Conference}, address = {PICC, Pasay City}, abstract = {In the field of physics, tensor networks have been successfully applied to solve for problems requiring high-dimensionality. As data required in data science are also high-dimensional, tensor methods have also gained appreciation as a tool in machine learning. In this study, we have utilized an existing tensor network-based machine learning program to investigate on the role of bond dimension in the learning rate and the learning accuracy in an image classification problem. In our simulation, the increase in bond dimension leads to improved accuracy but easily reached a saturation point where the gains are overshadowed by the computational cost.}, author = {Mykhal Gideoni L. Mangada and Francis N. C. Paraan} } @inproceedings {canoy, title = {Average work done in a ground state quantum quench of the Kitaev chain model with variable-range interactions}, booktitle = {Proceedings of the 36th Samahang Pisika ng Pilipinas Physics Conference}, year = {2018}, month = {6{\textendash}9 June 2018}, pages = {SPP-2018-PC-18}, address = {Puerto Princesa City, Philippines}, abstract = {We study the average work done associated with a ground state quantum quench of the Kitaev chain model with variable-range interactions. We do this by initially preparing an isolated quantum system in the ground state of the initial Hamiltonian at zero temperature. We, then, abruptly change the relative chemical potential parameter. The average work done on the system, which is defined as the difference between the measured energies before and after the quench, is derived and shown to have inflection points at the critical values of the relative chemical potential of the initial Hamiltonian.}, url = {https://paperview.spp-online.org/proceedings/article/view/SPP-2018-PC-18}, author = {Raymart Jay E. Canoy and Francis N. C. Paraan} } @inproceedings {476, title = {Band structure contribution of adsorbed H$_{2}$ on graphene calculated from molecular orbital projections}, booktitle = {Proceedings of the 36th Samahang Pisika ng Pilipinas Physics Conference}, year = {2018}, month = {6{\textendash}9 June 2018}, pages = {SPP-2018-PA-19}, address = {Puerto Princesa City, Philippines}, abstract = {Density functional theory allows for the first-principles calculation of projected wavefunctions onto orthogonalized atomic wavefunctions. Such calculations can be applied to study the bonding of a molecule onto an adsorbing surface. In particular, these projections allow one to identify the contributions of the adsorbed molecule to the band structure of the whole system. In this paper, we consider a system composed of an H2 molecule adsorbed onto the hollow (H) site in a graphene 3x3 supercell. The adsorbed H2 molecule gives rise to two bands roughly 6 eV on either side of the Fermi energy. These bands may be attributed to the hybridization of the H2 bonding and anti-bonding molecular\ σ\ orbitals and the graphene bands.
}, url = {https://paperview.spp-online.org/proceedings/article/view/SPP-2018-PA-19}, author = {Mario Antonio T. Ongkiko and Francis N. C. Paraan} } @inproceedings {464, title = {Benchmarking a tensor network-based machine learning algorithm for supervised image classification}, booktitle = {Proceedings of the 36th Samahang Pisika ng Pilipinas Physics Conference}, year = {2018}, month = {6{\textendash}9 June 2018}, pages = {SPP-2018-PB-23}, address = {Puerto Princesa City, Philippines}, abstract = {Real-world data is often scarce and the careful setting of hyperparameters to efficiently train machine learning algorithms is necessary. In this study the role of bond dimension on the performance of an existing tensor network-based machine learning program was benchmarked on the MNIST and fashion-MNIST data sets. In particular, the effects of bond dimension on the accuracy and execution times of the algorithm were investigated. Results show that a bond dimension of less than 100 is sufficient to reach an acceptable classification accuracy, and increasing the bond dimension further extends the execution time and consumes prohibitive amounts of memory without providing a reasonable improvement in accuracy.}, url = {https://paperview.spp-online.org/proceedings/article/view/SPP-2018-PB-23}, author = {Mykhal Gideoni L. Mangada and Francis N. C. Paraan} } @conference {478, title = {Calculation of the stiffness coefficients and elastic moduli of copper-silver alloy using molecular dynamics simulations}, year = {2018}, month = {18{\textendash}19 June 2018}, pages = {F3-5}, publisher = {ASTHRDP Graduate Scholars{\textquoteright} Conference}, address = {PICC, Pasay City}, abstract = {The elastic moduli for different atomic compositions of copper-silver binary alloy were numerically calculated and analyzed using elastic stiffness coefficients acquired from performing molecular dynamics simulations that use embedded atom model potentials. Constant strain rate along different crystallographic directions was employed to obtain the elastic stiffness coefficients while considering the anisotropic behavior of the material. Dependence of the elastic moduli on the atomic composition of copper-silver in selected ranges from 20-80\% and the effect of temperatures from 300-600 K on these properties were also investigated. It is found out that the elastic moduli increase with increasing copper concentration while decreases in value as temperature is increased.}, author = {Jan Fronimarc D. Viloria and Francis N. C. Paraan} } @conference {477, title = {Characterization of a ground state quantum quench of the Kitaev chain model with variable-range interactions using work statistics}, year = {2018}, month = {18{\textendash}19 June 2018}, pages = {F3-2}, publisher = {ASTHRDP Graduate Scholars{\textquoteright} Conference}, address = {PICC, Pasay City}, abstract = {We study the work statistics associated with a ground state quantum quench of the Kitaev chain model with variable-range interactions. We do this by initially preparing a system in the ground state of the Hamiltonian at zero temperature. The relative chemical potential parameter, which governs the unbalance between the chemical potential and hopping terms, is then abruptly changed. The variables of the work statistics, i.e., the average work done and work fluctuation, are derived. The average work done and work fluctuations are shown to have inflection points and kinks, respectively, which signal the vanishing of the excitation gap at the critical prequench relative chemical potential.}, author = {Raymart Jay E. Canoy and Francis N. C. Paraan} } @inproceedings {458, title = {Comparison of Python GPU implementations of eigensolvers}, booktitle = {Proceedings of the 36th Samahang Pisika ng Pilipinas Physics Conference}, year = {2018}, month = {6{\textendash}9 June 2018}, pages = {SPP-2018-PB-51}, address = {Puerto Princesa City, Philippines}, abstract = {Python implementations of GPU-based eigensolvers were tested and evaluated. The performance of PyCUDA and scikit-cuda library functions for Python were used and compared to the corresponding ones from the NumPy library. Despite GPU-based cuBLAS routines being faster than their usual NumPy equivalents on the consumer-level hardware used, cuSOLVER function implementations have longer execution times than the NumPy functions. Two Python variants of the tridiagonalization step of the Lanczos algorithm were tested with cuBLAS functions and we showed that a hybrid CPU-GPU approach resulted in an algorithm that was both fast and stable. However, the presented algorithms are still slower than the highly optimized NumPy eigensolver and further optimizations are needed to obtain GPU acceleration in our Python-based eigensolver.}, url = {https://paperview.spp-online.org/proceedings/article/view/SPP-2018-PB-51}, author = {John Ian Kenneth E. Felismino and Francis N. C. Paraan} } @inproceedings {467, title = {Computational fluid dynamics analysis of lift on the Teardrop 2.0 for different angles of attack}, booktitle = {Proceedings of the 36th Samahang Pisika ng Pilipinas Physics Conference}, year = {2018}, month = {6{\textendash}9 June 2018}, pages = {SPP-2018-2C-04}, address = {Puerto Princesa City, Philippines}, abstract = {The Teardrop 2.0 is a towed, wing shaped device used for the underwater surveying of shallow coral reefs. We use computational fluid dynamics (CFD) to examine the lift forces acting on a model of the Teardrop 2.0 and determine its lift coefficient for different angles of attack. In this study, a full scale computer generated reconstruction of the Teardrop 2.0 is subjected to fluid tunnel simulations using CFD software. It is found that lift is greatest at an attack angle of around 25{\textdegree}. At greater angles of attack, large regions of recirculation form behind the wing. This effect reduces flow past the trailing edge of the wing, causing lift to decrease. The resulting lift coefficient curve is found to be consistent with experimentally determined lift coefficient curves for flat plate wings.}, url = {https://paperview.spp-online.org/proceedings/article/view/SPP-2018-2C-04}, author = {Matthew R. Medrano and Maricor N. Soriano and Francis N. C. Paraan} } @inproceedings {488, title = {Density functional theory-based determination of the mechanism of electrochemical reduction of CO$_{2}$ to CO by Co(salen) complex}, booktitle = {Proceedings of the 36th Samahang Pisika ng Pilipinas Physics Conference}, year = {2018}, month = {6{\textendash}9 June 2018}, pages = {SPP-2018-PA-27}, address = {Puerto Princesa City, Philippines}, abstract = {We examine a possible mechanism for the electrochemical reduction of carbon dioxide to carbon monoxide with cobalt salen complex, Co(salen), as the catalyst. Density functional theory was used to calculate the ground state energies and reaction energies of possible reaction intermediates. The results indicate that the reduction from [Co(salen)-CO2]- to Co(salen)-CO proceeds via a Co(salen)-COOH intermediate through a proton transfer and a subsequent concerted proton-electron transfer that releases one molecule of water. The catalyst is then regenerated after carbon monoxide dissociates from the complex.
}, url = {https://paperview.spp-online.org/proceedings/article/view/SPP-2018-PA-27}, author = {Meliton R. Chiong III and Francis N. C. Paraan} } @inproceedings {450, title = {Entanglement spectrum and entropy scaling in a Kitaev chain with variable-range interaction}, booktitle = {Proceedings of the 36th Samahang Pisika ng Pilipinas Physics Conference}, year = {2018}, month = {6{\textendash}9 June 2018}, pages = {SPP-2018-PC-35}, address = {Puerto Princesa City, Philippines}, abstract = {The entanglement spectrum was calculated for a contiguous block of spins in a Kitaev chain with a power law decay of interactions. Changes in the degeneracies of the four largest eigenvalues of the spectrum identify the quantum critical line separating the paramagnetic and anti-ferromagnetic phases of the model. Effective central charges along the critical lines are calculated by analyzing the finite-size scaling of the entanglement entropy with block length. For power law exponents that correspond to short-ranged interactions the effective central charge is that of free-fermionic models. For longer ranged interactions the obtained central charge deviates from this value.}, url = {https://paperview.spp-online.org/proceedings/article/view/SPP-2018-PC-35}, author = {Cleofe Dennielle P. Ayang-ang and Francis N. C. Paraan} } @inproceedings {462, title = {Evaluating the performance of a thresholding filter on handwritten images classification task}, booktitle = {Proceedings of the 36th Samahang Pisika ng Pilipinas Physics Conference}, year = {2018}, month = {6{\textendash}9 June 2018}, pages = {SPP-2018-PB-47}, address = {Puerto Princesa City, Philippines}, abstract = {In this paper we evaluate the effect of a thresholding filter on the accuracy and training times of a deep neural network. The filter increases the brightness of each pixel in the input image and then applies a threshold condition that zeroes out values exceeding a preset value. Although the filter is lossy, we demonstrate improved learning performance under some use cases.}, url = {https://paperview.spp-online.org/proceedings/article/view/SPP-2018-PB-47}, author = {Vidal Wyatt M. Lopez and Francis N. C. Paraan} } @inproceedings {455, title = {GPU implementation of singular value decomposition for high rank tensors}, booktitle = {Proceedings of the 36th Samahang Pisika ng Pilipinas Physics Conference}, year = {2018}, month = {6{\textendash}9 June 2018}, pages = {SPP-2018-PB-50}, address = {Puerto Princesa City, Philippines}, abstract = {Programming using the Python API (application programming interface) offers some advantages over using compiled languages. Here we implement a high rank tensor decomposition routine using the TensorFlow library which has native support for utilizing multi-core CPU, GPU, and TPU hardware. Specifically, a singular value decomposition algorithm was performed on a rank-5 tensor. The performance of this Python implementation was compared with a known C++ based library written specifically for tensor manipulations but without native GPU support. We report some use cases where the implementation on a consumer grade GPU was empirically faster than the C++ based library when the rank-5 tensor has more than 2x10E6 elements. With the acceptable performance of the implementation, it may be beneficial to have have a native implementation of tensor network operations on TensorFlow.}, url = {https://paperview.spp-online.org/proceedings/article/view/SPP-2018-PB-50}, author = {Kryzz Joshua G. de Leon and Francis N. C. Paraan} } @inproceedings {451, title = {Ground state correlation functions of the XY spin chain in a random transverse field}, booktitle = {Proceedings of the 36th Samahang Pisika ng Pilipinas Physics Conference}, year = {2018}, month = {6{\textendash}9 June 2018}, pages = {SPP-2018-PB-44}, address = {Puerto Princesa City, Philippines}, abstract = {The single-body and anomalous (pair) correlation functions of Jordan-Wigner fermions in the ground state of a disordered XY chain are calculated. Disorder is introduced into this system as a site-dependent transverse field taken from a uniform distribution of fixed width and within the ferromagnetic phase. Results show that increasing the disorder strength by increasing the distribution width leads to a more rapid decay of correlations within the bulk. The average local transverse magnetization of the spin chain decreases with increasing disorder strength, having greater fluctuations in the middle bulk of the chain.}, url = {https://paperview.spp-online.org/proceedings/article/view/SPP-2018-PB-44}, author = {Binladin A Balt and Francis N. C. Paraan} } @inproceedings {457, title = {Ground state entanglement entropy between harmonically confined dipoles}, booktitle = {Proceedings of the 36th Samahang Pisika ng Pilipinas Physics Conference}, year = {2018}, month = {6{\textendash}9 June 2018}, pages = {SPP-2018-PB-53}, address = {Puerto Princesa City, Philippines}, abstract = {We calculate the R{\'e}nyi entanglement entropy between two harmonically confined dipoles when the degrees of freedom associated with one dipole is traced out in the ground state. When the dimer is in a bound state, the ground state wavefunction is a product of two-mode squeezed states and an exact expression for the R{\'e}nyi entanglement entropy is obtained. The entanglement entropy decays as a power of the separation distance between the dipoles and is a maximum at a critical length determined by the effective Bohr radius of the charge and the confinement length of the trapping potential.}, url = {https://paperview.spp-online.org/proceedings/article/view/SPP-2018-PB-53}, author = {Mignon Frances A. Dumanjog and Francis N. C. Paraan} } @inproceedings {456, title = {Ground state entanglement entropy in a coupled spin-1/2 dimer with Dzyaloshinsky-Moriya interaction}, booktitle = {Proceedings of the 36th Samahang Pisika ng Pilipinas Physics Conference}, year = {2018}, month = {6{\textendash}9 June 2018}, pages = {SPP-2018-PB-52}, address = {Puerto Princesa City, Philippines}, abstract = {We study the ground state entanglement entropy in a spin-1/2 dimer with Dzyaloshinsky-Moriya (DM) and Heisenberg interactions in a Zeeman field. For a fixed magnitude of the DM vector, the ground state entanglement entropy increases from the ferromagnetic to the anti-ferromagnetic limits of the Heisenberg interaction. In the case of anti-ferromagnetic interactions with strong Zeeman splitting there exists a non-zero value of the DM magnitude that minimizes ground state entanglement. A region of the ground state phase diagram is also described where a critical DM magnitude separates separable and maximally entangled ground states.}, url = {https://paperview.spp-online.org/proceedings/article/view/SPP-2018-PB-52}, author = {Rafael S. dela Rosa and Francis N. C. Paraan} } @inproceedings {449, title = {Piezoelectric tensor of AlN calculated by the Berry phase approach implemented in Quantum ESPRESSO}, booktitle = {Proceedings of the 36th Samahang Pisika ng Pilipinas Physics Conference}, year = {2018}, month = {6{\textendash}9 June 2018}, pages = {SPP-2018-PB-12}, address = {Puerto Princesa City, Philippines}, abstract = {The proper piezoelectric tensor of AlN was determined using the changes of the Berry phases in response to axial and shear strains in the linear regime. Phases arose from the variation of the wavevector of the Bloch states. Calculations were done in the Quantum ESPRESSO software package using Vanderbilt{\textquoteright}s formulation of the proper piezoelectric tensor. The maximum longitudinal piezoelectric modulus |eij|max coefficient of 1.461 C/m2 was found when both the change in the Berry phase and strain were along the c-axis.
}, url = {https://paperview.spp-online.org/proceedings/article/view/SPP-2018-PB-12}, author = {Paul Daniel S. Ang and Francis N. C. Paraan} } @inproceedings {461, title = {Symmetry-protection in the deformed Affleck-Kennedy-Lieb-Tasaki state}, booktitle = {Proceedings of the 36th Samahang Pisika ng Pilipinas Physics Conference}, year = {2018}, month = {6{\textendash}9 June 2018}, pages = {SPP-2018-PB-18}, address = {Puerto Princesa City, Philippines}, abstract = {The Haldane phase captured by the Affleck-Kennedy-Lieb-Tasaki (AKLT) state is a symmery-protected topological (SPT) phase protected by a set of symmetries: either inversion symmetry (IS), time-reversal symmetry (TRS) or the dihedral group of p rotations about two orthogonal axes (D2). This symmetry-protection follows from how the state transforms in its matrix product state (MPS) form under a certain symmetry operation. We study the q-deformed AKLT (AKLTq) state which also has a known MPS form that continuously transforms to that of an AKLT state and how this symmetry-protection is altered. We show that the AKLTq state can be adiabatically connected to the AKLT state when IS is protected. However, our approach does not conclusively lead to the similar conclusion for TRS and D2 , hence, we discuss possible explanations.}, url = {https://paperview.spp-online.org/proceedings/article/view/SPP-2018-PB-18}, author = {Gene M M Itable and Francis N. C. Paraan} } @inproceedings {chiong, title = {Ab initio study on the binding of carbon dioxide to cobalt salen complex}, booktitle = {Proceedings of the 35th Samahang Pisika ng Pilipinas Physics Conference}, year = {2017}, month = {7{\textendash}10 June 2017}, pages = {SPP-2017-3B-05}, address = {Cebu City, Philippines}, abstract = {Metal-organic complexes, such as metal-Schiff bases, can function as catalysts for electrochemical reduction. In this work we present first principles electronic structure calculations for the adduct formation involving carbon dioxide (CO2) and cobalt salen [Co(salen)] complex. Binding energy calculations show that carbon dioxide forms a stable adduct with [Co(salen)]$^{-}$ complex. The bonding between carbon dioxide and the cobalt metal center involves back-bonding mainly between the metal dz2 orbital and the π* orbital of CO2. An accompanying partial charge transfer from Co to CO2 was observed. This study can be used as a preliminary result to further study the structure and stability of other cobalt-carbon complexes.}, url = {http://paperview.spp-online.org/proceedings/article/view/152}, author = {Meliton R. Chiong III and Francis N. C. Paraan} } @conference {chiong2017, title = {Ab initio study on the effects of phenyl substitution on the binding of carbon dioxide to salcomine}, year = {2017}, month = {24{\textendash}26 May 2017}, pages = {147}, publisher = {12th Siam Physics Congress}, address = {Rayong, Thailand}, abstract = {Metal-organic complexes, such as metal-porphyrins, can function as homogeneous catalysts for electrochemical reduction. In this work we present ab initio electronic structure calculations for a reaction involving carbon dioxide and salcomine, a coordination complex consisting of a salen ligand and a cobalt (II) atom. Changes to the binding energy due to substitutions on the phenyl ring by different functional groups are also studied. Cases where a shrinking HOMO-LUMO gap decreases the overpotential and increases the catalytic efficiency of the complex are analyzed. This study provides a theoretical basis for possible salen complex candidates as electrocatalyst for the reduction of carbon dioxide.}, url = {https://indico.cern.ch/event/486350/contributions/2493722/}, author = {Meliton R. Chiong III and Francis N. C. Paraan} } @conference {canoy2017, title = {Block purity in a long-range Kitaev chain}, year = {2017}, month = {24{\textendash}25 May 2017}, pages = {153}, publisher = {2nd International Science Graduate Scholars{\textquoteright} Conference}, address = {PICC, Pasay City}, abstract = {The purity of blocks of 10- and 30-spins in a long-range Kitaev model is calculated by exact diagonalization. The obtained block purity is a measure of entanglement and number fluctuations between the block and the chain it is embedded in. A phase diagram is constructed from the purity when it is expressed as a function of the range parameter and relative chemical potential. It is found that the block purity can differentiate between the magnetic phases of the long-range Kitaev model: it is small in the region corresponding to the antiferromagnetic phase and large in the paramagnetic region.}, author = {Raymart Jay E. Canoy and Francis N. C. Paraan} } @inproceedings {esperanza, title = {Correlations in an extended Hubbard model with Ising-like interaction}, booktitle = {Proceedings of the 35th Samahang Pisika ng Pilipinas Physics Conference}, year = {2017}, month = {7{\textendash}10 June 2017}, pages = {SPP-2017-PB-08}, address = {Cebu City, Philippines}, abstract = {Density-density and spin-spin correlations are calculated in an extended Hubbard model with an intersite Ising-like interaction. Local expectation values and correlation functions involving charge density and magnetization are obtained using the density matrix renormalization group (DMRG) for a periodic chain of L = 10 sites at half-filling. Antiferromagnetic phases with spin and charge density modulation are identified and located in a phase diagram.}, url = {http://paperview.spp-online.org/proceedings/article/view/56}, author = {Robertson C. Esperanza and Francis N. C. Paraan} } @conference {434, title = {A DFT-based determination of the mechanism of electrochemical reduction of CO$_{2}$ to CO by a cobalt-Schiff base catalyst}, year = {2017}, month = {8{\textendash}10 Nov 2017}, pages = {P024}, publisher = {9th Electronic Structure and Processes at Molecular-Based Interfaces Workshop}, address = {National University of Singapore, Singapore}, abstract = {We perform density functional theory (DFT) based calculations to investigate the reduction of carbon dioxide CO2 to carbon monixide CO using a cobalt-Schiff base catalyst, Co(salen). DFT calculated formation energies and reduction potentials showed that CO2 is reduced to CO via a [Co(salen)-COOH] intermediate. The first step of the mechanism involves the reduction of electrically neutral [Co(salen)]\ to [Co(salen)]-\ anion, followed by an electrophilic addition of CO2. Furthermore, the sigma bond formed between cobalt metal center and\ CO2\ involves a back-donation and partial charge transfer from cobalt to carbon. [Co(salen)-COOH] is further reduced to [Co(salen)-CO] and CO is released from the catalyst along with water H2O.
}, author = {Meliton R. Chiong III and Francis N. C. Paraan} } @conference {432, title = {Entanglement between spin and orbital degrees of freedom in a 2D electron gas}, year = {2017}, month = {18{\textendash}22 Sept 2017}, pages = {1}, publisher = {International Workshop on Non-linear Effects and Short-time Dynamics in Novel Superconductors and Correlated Spin-orbit Coupled Systems}, address = {Daejeon, South Korea}, abstract = {The Rashba interaction couples spin and orbital degrees of freedom in a two-dimensional electron gas. A Landau level basis leads to an equivalent spin-boson model that couples adjacent Landau levels. We study the entanglement between the spin and orbital subspaces in the ground state of a gas of electrons described by this Hamiltonian. The spin-orbit entanglement entropy as a function of filling factor is piecewise smooth with discontinuous derivatives due to gapped levels of degenerate orbitals and level crossings.}, url = {http://pcs.ibs.re.kr/PCS_Workshops/PCS_NLST2017.html}, author = {Francis N. C. Paraan and Rona F Barbarona} } @conference {435, title = {Entanglement entropy in a spin-boson model and level crossings in an Ising dimer with Dzyaloshinskii-Moriya interaction}, year = {2017}, month = {20{\textendash}24 Nov 2017}, pages = {P.11}, publisher = {2017 ICTP Asian Network School and Workshop on Complex Condensed Matter Systems}, address = {Institute of Physics, Vietnam Academy of Science and Technology, Hanoi, Vietnam}, abstract = {We calculate the entanglement entropy between a spin and bosonic modes in a spin-boson model using different ground state ansatze. The entanglement entropy saturates exponentially to a constant as the value of the displacement parameters of the boson modes is increased. We also search for level crossings in a system composed of two spins coupled by a Dzyaloshinkskii-Moriya interaction.}, url = {https://www.iop.vast.ac.vn/theor/conferences/asian/2017/program.php}, author = {Rafael S. dela Rosa and Francis N. C. Paraan} } @inproceedings {ang, title = {Linear elastic and piezoelectric response of BaNiO3 to strain}, booktitle = {Proceedings of the 35th Samahang Pisika ng Pilipinas Physics Conference}, year = {2017}, month = {7{\textendash}10 June 2017}, pages = {SPP-2017-PB-36}, address = {Cebu City, Philippines}, abstract = {Preliminary ab initio calculations were done in Quantum ESPRESSO to obtain the piezoelectric coefficients of BaNiO3 by computing the stress and polarization induced by strain. The linear elastic response to strain was investigated under the six deformation modes to obtain full elastic stiffness tensor. A linear polarization response was found using the Berry-phase method. These results would be utilized in future work to calculate the piezoelectric coefficients of BaNiO3 and other perovskites.}, url = {http://paperview.spp-online.org/proceedings/article/view/209}, author = {Paul Daniel S. Ang and Francis N. C. Paraan} } @inproceedings {viloria, title = {Molecular dynamics calculation of the elastic constants of quenched FeNi and FeCr alloys}, booktitle = {Proceedings of the 35th Samahang Pisika ng Pilipinas Physics Conference}, year = {2017}, month = {7{\textendash}10 June 2017}, pages = {SPP-2017-2B-03}, address = {Cebu City, Philippines}, abstract = {Molecular dynamics simulations were conducted to obtain the elastic constants of quenched FeNi and FeCr alloys at different atomic compositions. The simulation was conducted using an embedded atom model (EAM) potential and the alloys were subjected to a rapid cooling from 1273 K to 298 K. Deformation process was performed along different crystallographic directions at a constant strain rate. The calculated elastic constants of quenched FeNi and FeCr alloys are in good agreement to experimental data with 1-12\% difference in values. Accuracy of the results were associated with the structural phase and transferability of the EAM potential at higher temperatures.}, url = {http://paperview.spp-online.org/proceedings/article/view/121}, author = {Jan Fronimarc D. Viloria and Francis N. C. Paraan} } @inproceedings {fernandez, title = {Molecular dynamics calculation of the reduced glass transition temperature for a copper-silver metallic glass}, booktitle = {Proceedings of the 35th Samahang Pisika ng Pilipinas Physics Conference}, year = {2017}, month = {7{\textendash}10 June 2017}, pages = {SPP-2017-2B-06}, address = {Cebu City, Philippines}, abstract = {A molecular dynamics simulation with an embedded atom method (EAM) potential was performed to simulate metallic glass formation in a 32000-atom cubic supercell of a Cu64 Ag36 alloy. The obtained cooling curve and pair distribution function possess features that support the formation of a metallic glass. The reduced glass transition temperature Trg was calculated to be 0.53, which passes the Turnbull criterion for good metallic glass formers.}, url = {http://paperview.spp-online.org/proceedings/article/view/123}, author = {Zed Harold E. Fernandez and Francis N. C. Paraan} } @conference {viloria2017, title = {Molecular dynamics study of the elastic properties of copper-silver alloy using embedded atom model potential}, year = {2017}, month = {24{\textendash}26 May 2017}, pages = {164}, publisher = {12th Siam Physics Congress}, address = {Rayong, Thailand}, abstract = {The elastic properties of copper-silver alloy were determined for different atomic compositions by molecular dynamics simulations using an embedded atom model (EAM) potential. The elastic constants (c11, c12, c44) that describe the Young{\textquoteright}s modulus, bulk modulus, and shear modulus, were obtained from the stress-strain curves using strains applied at a constant rate. The temperature dependence of the elastic properties from 300K to 600K is also reported.}, url = {https://indico.cern.ch/event/486350/contributions/2493723/}, author = {Jan Fronimarc D. Viloria and Francis N. C. Paraan} } @inproceedings {medrano, title = {Quantitative analysis of fluid flow around the Towpedo via computational fluid dynamics}, booktitle = {Proceedings of the 35th Samahang Pisika ng Pilipinas Physics Conference}, year = {2017}, month = {7{\textendash}10 June 2017}, pages = {SPP-2017-3B-04}, address = {Cebu City, Philippines}, abstract = {The Towpedo is a torpedo-shaped device used to conduct rapid and wide-range photographic surveys of shallow coral reefs. The objectives of this study were to determine the forces acting on a Towpedo moving in seawater and determine its drag coefficient via computational fluid dynamics. A computer generated model of the Towpedo was subjected to fluid tunnel simulations using computational fluid dynamic software. The results revealed regions of highest pressure at the nose of the Towpedo, while forces acting perpendicular to the direction of motion were relatively small compared to the drag force acting along the direction of flow. Resulting drag force was also found to exhibit a quadratic relationship with velocity, which is consistent with empirical models of drag. From these results, the drag coefficient of the Towpedo was determined.}, url = {http://paperview.spp-online.org/proceedings/article/view/213}, author = {Matthew R. Medrano and Apolinario Miguel I. Tan and Aaron T. Hilomen and Maricor N. Soriano and Francis N. C. Paraan} } @inproceedings {balt, title = {Quasi-particle excitation spectrum of an XY spin chain in a random transverse field}, booktitle = {Proceedings of the 35th Samahang Pisika ng Pilipinas Physics Conference}, year = {2017}, month = {7{\textendash}10 June 2017}, pages = {SPP-2017-PB-27}, address = {Cebu City, Philippines}, abstract = {The quasi-particle excitation spectrum of an XY spin chain in a random transverse field was calculated by an exact singular value decomposition. The spectrum was found to be robust at small disorder strengths and deep within the paramagnetic phase. For larger disorder strengths, and about the ferromagnetic region, the spectrum deviated further from the quasi-excitation spectrum of the ordered chain. These deviations lead to the disorder-averaged ground state energy E0 to increase with disorder strength, even as the average field strength remains constant.}, url = {http://paperview.spp-online.org/proceedings/article/view/170}, author = {Binladin A Balt and Francis N. C. Paraan} } @inproceedings {generalao, title = {Reducing execution times of Quantum ESPRESSO PWscf calculations by routing matrix multiplication calls to GPUs}, booktitle = {Proceedings of the 35th Samahang Pisika ng Pilipinas Physics Conference}, year = {2017}, month = {7{\textendash}10 June 2017}, pages = {SPP-2017-PB-05}, address = {Cebu City, Philippines}, abstract = {We report significant decreases in execution times of plane-wave self consistent field (PWscf) calculations on the software suite Quantum ESPRESSO (QE) by routing general matrix multiplication calls to graphical processing units. The approach described here does not require source code modifications nor recompilation. Running the standard benchmark test AUSURF112 on a single 2.0 Ghz core with two threads showed that using two commodity GPU cards can halve PWscf execution times.}, url = {http://paperview.spp-online.org/proceedings/article/view/222}, author = {Oliver B. Generalao and Francis N. C. Paraan} } @inproceedings {ayang-ang, title = {Schmidt gaps in a long-range Kitaev chain}, booktitle = {Proceedings of the 35th Samahang Pisika ng Pilipinas Physics Conference}, year = {2017}, month = {7{\textendash}10 June 2017}, pages = {SPP-2017-1C-04}, address = {Cebu City, Philippines}, abstract = {The Schmidt gap for a block of spins in an infinite long-range Kitaev chain is calculated as a function of interaction range and the relative strengths of the chemical potential and hopping terms. We find that for long-ranged interactions where area law violations to the entanglement entropy occur, the Schmidt gap does not appear to close rapidly with chain length. For short-ranged interactions however, the Schmidt gap vanishes in a parameter region corresponding to an antiferromagnetic phase with gapless edge modes. These results demonstrate that the Schmidt gap can be used to distinguish quantum phases in the long-range Kitaev model.}, url = {http://paperview.spp-online.org/proceedings/article/view/107}, author = {Cleofe Dennielle P. Ayang-ang and Francis N. C. Paraan} } @article {376, title = {Simple techniques for improving deep neural network outcomes on commodity hardware}, journal = {AIP Conf. Proc. (8th Jagna International Workshop)}, volume = {1871}, year = {2017}, pages = {040001 }, abstract = {We benchmark improvements in the performance of deep neural networks (DNN) on the MNIST data test upon implementing two simple modifications to the algorithm that have little overhead computational cost. First is GPU parallelization on a commodity graphics card, and second is initializing the DNN with random orthogonal weight matrices prior to optimization. Eigenspectra analysis of the weight matrices reveal that the initially orthogonal matrices remain nearly orthogonal after training. The probability distributions from which these orthogonal matrices are drawn are also shown to significantly affect the performance of these deep neural networks.}, doi = {10.1063/1.4996523}, url = {http://aip.scitation.org/doi/10.1063/1.4996523}, author = {Nicholas Christopher A Colina and Carlos E Perez and Francis N. C. Paraan} } @conference {sambo2017, title = {Spin correlation functions of the ground-state quenched XY model}, year = {2017}, month = {24{\textendash}25 May 2017}, pages = {153}, publisher = {2nd International Science Graduate Scholars{\textquoteright} Conference}, address = {PICC, Pasay City}, abstract = {We obtain exact expressions for the magnetizations and spin correlation functions for the ground-state quenched spin-1/2 XY model with both anisotropy and transverse magnetic field as quench parameters. The spin correlation functions were evaluated by Pfaffians of matrices with spinless fermionic operator correlations as elements. The transverse magnetization is obtained in the thermodynamic limit by the computation of a time-dependent density matrix. Non-analyticities in these quantities at some critical times are indicative of dynamical quantum phase transitions.}, author = {Jan Philippe B. Sambo and Francis N. C. Paraan} } @conference {430, title = {Strong chemisorption of CO on neutral B13 cluster edge site}, year = {2017}, month = {8{\textendash}11 Aug 2017}, pages = {PS-03}, publisher = {9th Conference of Asian Consortium on Computational Materials Science}, address = {Kuala Lumpur, Malaysia}, abstract = {We investigate the interaction of carbon monoxide (CO) molecule with neutral boron 13 (B13) cluster using spin-polarized density functional theory (DFT). We found that the edge sites of B13 cluster is the most reactive part, with strong CO adsorption of around -1.67 eV. Molecular orbitals analysis of the cluster shows that~the HOMO nearest to the Fermi level contributes to the adsorption of CO molecule. Our results indicate that~B13 cluster~could have potential applications in the storage and sequestration of CO molecules.}, url = {https://umconference.um.edu.my/accms-9}, author = {Alexandra B. Santos-Putungan and Nata{\v s}a Stoji{\'c} and Nadia Binggeli and Francis N. C. Paraan} } @inproceedings {felismino, title = {Wigner functions and uncertainty products from partially transposed Dicke model ground states}, booktitle = {Proceedings of the 35th Samahang Pisika ng Pilipinas Physics Conference}, year = {2017}, month = {7{\textendash}10 June 2017}, pages = {SPP-2017-PB-03}, address = {Cebu City, Philippines}, abstract = {Wigner functions are used to calculate position-momentum uncertainty products from partially transposed Dicke model ground states that are partitioned into atomic and photonic degrees of freedom. No violations of the canonical minimum uncertainty relation are observed. However, the position-momentum uncertainty product is seen to diverge as a power law as the quantum critical coupling strength is approached.}, url = {http://paperview.spp-online.org/proceedings/article/view/69}, author = {John Ian Kenneth E. Felismino and Francis N. C. Paraan} } @inproceedings {333, title = {Benchmarking GPU acceleration of a parallel molecular dynamics simulation}, booktitle = {Proceedings of the 34th Samahang Pisika ng Pilipinas Physics Congress}, year = {2016}, month = {18{\textendash}21 Aug 2016}, pages = {SPP-2016-PA-19}, address = {University of the Philippines Visayas, Iloilo City}, abstract = {The parallel speedup of component subroutines in a molecular dynamics simulation is measured after implementing MPI-based CPU parallelization and GPU acceleration. GPU acceleration was observed to yield an order of magnitude reduction in simulation times (13.9x{\textendash}23.6x relative to a serial run). Slightly less speedup is achieved by CPU parallelization (7.5x) over nine processors. Performance scaling is diminished by communication operations as the number of processes launched begin to exceed the number of available physical CPU cores.}, author = {Zed Harold E. Fernandez and Lloyd Francis L Co and Francis N. C. Paraan} } @inproceedings {338, title = {Block entanglement in the ground state of the Majumdar-Ghosh model}, booktitle = {Proceedings of the 34th Samahang Pisika ng Pilipinas Physics Congress}, year = {2016}, month = {18{\textendash}21 Aug 2016}, pages = {SPP-2016-PB-22}, address = {University of the Philippines Visayas, Iloilo City}, abstract = {We use matrix product state representations and transfer matrix methods to calculate the reduced density matrix of a block of spins in the ground state of the Majumdar-Ghosh spin chain. The full entanglement spectrum is obtained and the von Neumann entanglement entropy is expressed as a function of block length. We found that the von Neumann entropy increases exponentially fast as the length of the block increases and has a saturation value of Smax = ln 3.}, author = {Jade Farrah Dianne T Mendoza and Francis N. C. Paraan} } @article {374, title = {Detailed calculation of the average work done in a ground state quench of the quantum Ising model}, journal = {Science Diliman}, volume = {28:2}, year = {2016}, pages = {54-64}, abstract = {A detailed derivation of the exact expression for the average work done in a transverse field quench of the quantum Ising model ground state is presented. In the thermodynamic limit, it is proved that the average work done generally has inflection points at the critical field for the pre-quench quantum phase transition. The first divergent field derivative is calculated and is shown to diverge logarithmically. We also demonstrate that the average work done is equal to the product of the transverse magnetization of the pre-quench ground state and the change in the magnetic field.}, url = {http://www.journals.upd.edu.ph/index.php/sciencediliman/article/view/5509/4939}, author = {Salvador T Laurente Jr and Francis N. C. Paraan} } @conference {372, title = {Entanglement and fluctuations in the Majumdar-Ghosh model ground state}, year = {2016}, month = {4{\textendash}8 Dec 2016}, pages = {QUICC S1}, publisher = {Joint 13th Asia Pacific Physics Conference and 22nd Australian Institute of Physics Congress}, address = {Brisbane, Australia}, abstract = {The matrix product state representation of the ground state of the Majumdar{\textendash}Ghosh Model (MGM) is used to obtain the reduced density matrix of a block of x spins in a periodic MGM chain. This calculation leads to exact expressions for the entanglement entropy and subsystem fluctuations as a function of block length. We find that the entanglement entropy saturates exponentially to ln 3, even as the subsystem Hilbert space is five-dimensional.}, url = {http://aappsbulletin.org/myboard/read.php?Board=others\&id=100}, author = {Jade Farrah Dianne Mendoza and Francis N. C. Paraan} } @inproceedings {335, title = {Entanglement and ground state level crossings in an extended Hubbard dimer}, booktitle = {Proceedings of the 34th Samahang Pisika ng Pilipinas Physics Congress}, year = {2016}, month = {18{\textendash}21 Aug 2016}, pages = {SPP-2016-PB-20}, address = {University of the Philippines Visayas, Iloilo City}, abstract = {The single-site entanglement entropy in the ground state of an extended Hubbard dimer is calculated in terms of intrasite and intersite interaction parameters. Entanglement vanishes in a ferromagnetic regime characterized by a degenerate spin-polarized ground state. In parameter ranges with non-zero entanglement, the ground state is a linear combination of states with spin and charge modulation.}, author = {Robertson C. Esperanza and Francis N. C. Paraan} } @article {330, title = {Entanglement-fluctuation relation for bipartite pure states}, journal = {Phys. Rev. A}, volume = {94}, year = {2016}, pages = {022323}, abstract = {We identify subsystem fluctuations (variances) that measure entanglement in an arbitrary bipartite pure state. These fluctuations are of observables that generalize the notion of polarization to an arbitrary N-level subsystem. We express this polarization fluctuation in terms of subsystem purity and other entanglement measures. The derived entanglement-fluctuation relation is evaluated for the ground states of a one-dimensional free-fermion gas and the Affleck-Kennedy-Lieb-Tasaki spin chain. Our results provide a framework for experimentally measuring entanglement using Stern-Gerlach{\textendash}type state selectors.}, doi = {10.1103/PhysRevA.94.022323}, url = {http://link.aps.org/doi/10.1103/PhysRevA.94.022323}, author = {Aura Mae B Villaruel and Francis N. C. Paraan} } @inproceedings {313, title = {Importance of initialization of weight matrices in deep learning neural networks}, booktitle = {Proceedings of the 34th Samahang Pisika ng Pilipinas Physics Congress}, year = {2016}, month = {18{\textendash}21 Aug 2016}, pages = {SPP-2016-PA-21}, address = {University of the Philippines Visayas, Iloilo City}, abstract = {The success of deep neural networks relies on optimized weight matrices are initialized in different ways. This work reports learning improvement in a six-layer deep neural network that is initialized with orthogonal weight matrices when compared to other commonly-used initialization schemes. An analysis of the eigenvalue spectra of the optimized solutions implies that the space of orthogonal weight matrices lies close to the manifold of learned states.}, author = {Nicholas Christopher A Colina and Carlos E Perez and Francis N. C. Paraan} } @article {165, title = {Integer effects in the entanglement and spin fluctuations of a quantum Hall system with Rashba interactions}, journal = {J. Stat. Mech. Theor. Exp.}, volume = {2016}, year = {2016}, pages = {053104}, abstract = {We report distinctive nonanalytic signatures in the spin{\textendash}orbit entanglement of a 2D electron gas with Rashba interactions at integer values of the filling factor and at certain level crossings. The accompanying sharp changes in the bulk spin{\textendash}orbit entanglement entropy can be probed by measuring the fluctuation in the transverse spin polarization of the electron gas.
}, doi = {10.1088/1742-5468/2016/05/053104}, author = {Rona F Barbarona and Francis N. C. Paraan} } @inproceedings {309, title = {Investigation of neutral B13 clusters: A density functional theory study}, booktitle = {Proceedings of the 34th Samahang Pisika ng Pilipinas Physics Congress}, year = {2016}, month = {18{\textendash}21 Aug 2016}, pages = {SPP-2016-PA-18}, address = {University of the Philippines Visayas, Iloilo City}, abstract = {We investigate the electronic structure of neutral boron_13 (B13) clusters using spin-polarized density functional theory (DFT). The stable B13 cluster is observed to have a two-dimensional planar structure. Energy levels diagram shows that it has a highest occupied molecular orbital{\textendash}lowest unoccupied molecular orbital (HOMO-LUMO) gap of 0.36 eV. Analysis of the electronic charge density of the B13 cluster reveals that most of the electrons are shared between B atoms and are located at the edges, where the HOMO and LUMO are also localized. Our results indicate that the most reactive part of the cluster is along its edges.}, author = {Alexandra B. Santos-Putungan and Nata{\v s}a Stoji{\'c} and Nadia Binggeli and Francis N. C. Paraan} } @inproceedings {332, title = {Loschmidt amplitude zeros as a probe for criticality in the quenched XY model}, booktitle = {Proceedings of the 34th Samahang Pisika ng Pilipinas Physics Congress}, year = {2016}, month = {18{\textendash}21 Aug 2016}, pages = {SPP-2016-5C-06}, address = {University of the Philippines Visayas, Iloilo City}, abstract = {This paper investigates the correspondence between dynamical phase transitions (DPT) and quenches across quantum critical points (QCP) in ground state quenches of a spin-1/2 XY model. These DPTs are identified by treating the wavefunction overlap between pre- and post-quench states as a partition funtion and determining its Fisher zeros. It is found that DPTs do not always occur when the quench crosses a quantum critical line. A general condition for the occurrence of these DPTs in the XY model is derived.}, author = {Jan Philippe B. Sambo and Francis N. C. Paraan} } @inproceedings {322, title = {Molecular dynamics of rapid melting in a copper-silver alloy}, booktitle = {Proceedings of the 34th Samahang Pisika ng Pilipinas Physics Congress}, year = {2016}, month = {18{\textendash}21 Aug 2016}, pages = {SPP-2016-PA-22}, address = {University of the Philippines Visayas, Iloilo City}, abstract = {A copper-silver alloy (64\% Cu / 36\% Ag atomic ratio) is simulated by molecular dynamics. The alloy is subjected to rapid linear heating protocols from room temperature to 2100 K at several ramp rates of the order ~K/ps. Numerical evidence for a first-order melting transition at 1.19 x 10^3 K is observed. This elevated value is suggested to be the result of high pressures in the microscopic sample.}, author = {Cleofe Dennielle P. Ayang-ang and John Joseph S Solo and Zed Harold E. Fernandez and Francis N. C. Paraan} } @inproceedings {311, title = {Molecular dynamics simulation of liquid gallium using an embedded atom model}, booktitle = {Proceedings of the 34th Samahang Pisika ng Pilipinas Physics Congress}, year = {2016}, month = {18{\textendash}21 Aug 2016}, pages = {SPP-2016-5B-03}, address = {University of the Philippines Visayas, Iloilo City}, abstract = {Optimized embedded atom model (EAM) potential parameters from the literature are used to perform a molecular dynamics simulation of liquid gallium. Liquid densities are calculated at several temperatures at a fixed pressure of 1 atm to determine the mean coefficient of thermal expansion. Radial pair distribution functions showing the shell structure of the liquid phase are also obtained and compared with previous simulations and experimental results.}, author = {Oliver B. Generalao and Allan Jay Pari{\~n}as and Francis N. C. Paraan} } @inproceedings {314, title = {Multispecies fluid flow simulations inside a chamber via computational fluid dynamics}, booktitle = {Proceedings of the 34th Samahang Pisika ng Pilipinas Physics Congress}, year = {2016}, month = {18{\textendash}21 Aug 2016}, pages = {SPP-2016-2C-04}, address = {University of the Philippines Visayas, Iloilo City}, abstract = {Computational fluid dynamics simulations of silane inside a two-dimensional container filled with nitrogen gas were performed using finite element methods. Pressure gradients were introduced to the system, and the time needed for the system to reach dynamic equilibrium for mass fractions, pressure, and velocity was determined. The inlet size was also varied to determine how it affects the equilibriation time.}, author = {Apolinario Miguel I. Tan and Nicholas Christopher A Colina and Jennifer Anne Constantino and Francis N. C. Paraan} } @inproceedings {spvm-2016-1, title = {Observation of the behavior and properties of the critical micelle concentration (CMC) at different temperatures}, booktitle = {Proceedings of the 18th Samahang Pisika ng Visayas at Mindanao National Physics Conference}, year = {2016}, month = {20{\textendash}22 Oct 2016}, pages = {13}, address = {Silliman University, Dumaguete City}, author = {Allan Jay L Pari{\~n}as and John Joseph S Solo and Lloyd Francis L Co and Francis N. C. Paraan} } @inproceedings {310, title = {Parallelization benchmarks of plane wave self-consistent field calculations on an IBM BlueGene supercomputer}, booktitle = {Proceedings of the 34th Samahang Pisika ng Pilipinas Physics Congress}, year = {2016}, month = {18{\textendash}21 Aug 2016}, pages = {SPP-2016-PB-19}, address = {University of the Philippines Visayas, Iloilo City}, abstract = {A plane wave self-consistent field calculation was parallelized over two node cards of an IBM BlueGene/P supercomputer. A maximum speedup of 9x was measured in Virtual Node execution mode. The observed performance improvements are consistent with Amdahl{\textquoteright}s law for an algorithm that is approximately 89\% parallelizable.}, author = {Paul Daniel S. Ang and Lean Louiel A Peria and Joshua Gregor A Dizon and Francis N. C. Paraan} } @inproceedings {331, title = {Piezomagnetic properties and band structure of Mn3GaN calculated using density functional theory}, booktitle = {Proceedings of the 34th Samahang Pisika ng Pilipinas Physics Congress}, year = {2016}, month = {18{\textendash}21 Aug 2016}, pages = {SPP-2016-3A-06}, address = {University of the Philippines Visayas, Iloilo City}, abstract = {The antiperovskite Mn3GaN in the Γ-5g configuration has a noncollinear magnetic ordering and exhibits the piezomagnetic effect. This study aims to replicate previous ab initio studies of Mn3GaN. Magnetic moments are allowed to relax after applying various amounts of strain. Results show that the total magnetization varies linearly with strain up to {\textpm}2\%. The observed response of the magnetization was stronger for negative strain than for positive strain. Calculations reveal that this net magnetization arises from the strain-induced rotation of the local magnetic moments associated with each Mn atom. In addition, numerical calculations of the band structure and density of states of Mn3GaN are presented.}, author = {Lean Louiel A Peria and Paul Daniel S. Ang and Francis N. C. Paraan} } @conference {351, title = {Polarization fluctuation as an entanglement measure for N-level systems}, year = {2016}, month = {7{\textendash}8 Apr 2016}, pages = {127}, publisher = {1st International DOST-SEI ASTHRDP-NSC Scholars{\textquoteright} Conference}, address = {PICC, Pasay City}, abstract = {It is known that subsystem fluctuations are related to entanglement for any N-level system entangled with an environment. We define an observable wherein its fluctuations can be directly related to known measures such as the purity, R{\'e}nyi-2 entropy, and concurrence. This quantity, which we call the Schmidt polarization fluctuation shows an exact relationship between fluctuations and entanglement that is simple to construct and is model-independent. It can also be considered as a proper entanglement measure and is experimentally accessible.}, author = {Aura Mae B Villaruel and Francis N. C. Paraan} } @conference {325, title = {Quantum criticality in a quenched XY chain}, year = {2016}, month = {25{\textendash}27 Jul 2016}, publisher = {Conference on Entanglement and Non-Equilibrium Physics of Pure and Disordered Systems}, address = {International Centre for Theoretical Physics, Trieste}, url = {http://indico.ictp.it/event/7604/}, author = {Francis A Bayocboc Jr and Jan Philippe Sambo and Francis N. C. Paraan} } @conference {paraan-qpcmp-2016, title = {Quenched spin chains and generalized Gibbs ensembles}, year = {2016}, month = {18{\textendash}19 Apr 2016}, publisher = {Workshop on Theories in Quantum Phenomena and Condensed Matter Physics}, address = {University of the Philippines Los Ba{\~n}os, Laguna}, url = {https://imsp.uplb.edu.ph/index.php/23-imsp-news/training-and-conference/386-quantum-phenomena-workshop}, author = {Francis N. C. Paraan} } @inproceedings {spvm-2016-2, title = {Structural analysis and visualization of spatial distribution of electrons of pristine and alkali metal-doped polythiophene}, booktitle = {Proceedings of the 18th Samahang Pisika ng Visayas at Mindanao National Physics Conference}, year = {2016}, month = {20{\textendash}22 Oct 2016}, pages = {23}, address = {Silliman University, Dumaguete City}, author = {Prudence Peace V Bustamante and Melchor J Potestas and Francis N. C. Paraan} } @conference {371, title = {Zeros of the Loschmidt amplitude in the quenched XY model}, year = {2016}, month = {4{\textendash}8 Dec 2016}, pages = {CSCMP 48}, publisher = {Joint 13th Asia Pacific Physics Conference and 22nd Australian Institute of Physics Congress}, address = {Brisbane, Australia}, abstract = {We investigate the notion of dynamical quantum phase transitions (DQPTs) in the quenched ground state of the spin-1/2 XY model H(h0, γ0) to H(h1, γ1). By a Wick rotation, the Loschmidt amplitude is formally treated as a canonical partition function and its zeros used as a probe for criticality. This approach is similar to that used in a Fisher zero analysis in identifying classical phase transitions. The occurrence of real-time zeros for the Loschmidt amplitude signify DQPTs. Previously, a correspondence between DQPTs and quenches across critical points was observed for the transverse-field Ising model. The zeros of the Loschmidt amplitude in a quench of the XY model ground state was calculated and the corresponding condition for a DPQT to occur was derived for a generic quench. It can be observed that not all quenches across critical points are accompanied by DQPTs and vice versa. This result is consistent with previous studies of the quenched XY model.}, url = {http://aappsbulletin.org/myboard/read.php?Board=others\&id=100}, author = {Jan Philippe Sambo and Francis N. C. Paraan} } @article {Seroje2015, title = {Effective thermodynamics of isolated entangled squeezed and coherent states}, journal = {Eur. J. Phys.}, volume = {36}, number = {5}, year = {2015}, pages = {055051}, abstract = {The R{\'e}nyi entanglement entropy is calculated exactly for mode-partitioned isolated systems such as the two-mode squeezed state and the multi-mode Silbey{\textendash}Harris polaron ansatz state. Effective thermodynamic descriptions of the correlated partitions are constructed to present quantum information theory concepts in the language of thermodynamics. Boltzmann weights are obtained from the entanglement spectrum by deriving the exact relationship between an effective temperature and the physical entanglement parameters. The partition function of the resulting effective thermal theory can be obtained directly from the single-copy entanglement.}, doi = {10.1088/0143-0807/36/5/055051}, author = {King Karl R Seroje and Rafael S. dela Rosa and Francis N. C. Paraan} } @inproceedings {santosputungan-spp-2015, title = {Enhanced ferromagnetism in Zn0.5 (Co)0.5 O alloy: DFT calculations}, booktitle = {Proceedings of the 33rd Samahang Pisika ng Pilipinas Physics Congress}, year = {2015}, month = {3{\textendash}6 Jun 2015}, pages = {SPP-2015-PA-14}, address = {University of Northern Philippines, Vigan City}, abstract = {We quantify the extractable entanglement of excited states of a Lieb-Liniger gas that are obtained from coarse-grained measurements on the ground state in which the boson number in one of two complementary contiguous partitions of the gas is determined. Numerically exact results obtained from the coordinate Bethe ansatz show that the von Neumann entropy of the resulting bipartite pure state increases monotonically with the strength of repulsive interactions and saturates to the impenetrable-boson limiting value. We also present evidence indicating that the largest amount of entanglement can be extracted from the most probable projected state having half the number of bosons in a given partition. Our study points to a fundamental difference between the nature of the entanglement in free-bosonic and free-fermionic systems, with the entanglement in the former being zero after projection, while that in the latter (corresponding to the impenetrable-boson limit) being nonzero.
}, doi = {10.1103/PhysRevA.84.032330}, author = {Francis N. C. Paraan and Javier Molina-Vilaplana and Vladimir E Korepin and Sougato Bose} } @article {Paraan2010, title = {Perturbative correction to the ground-state properties of one-dimensional strongly interacting bosons in a harmonic trap}, journal = {Phys. Rev. A}, volume = {82}, number = {6}, year = {2010}, note = {cited By 2}, pages = {065603}, abstract = {